Well, lots of replies from the Ram guy's
I have the same truck and hitch as you. Triple E Topaz 27' fifth wheel with a 18' Lund fisherman 1800 in tow.
I have my Andersen hitch connected to the factory prep and a GM bed mat. The ball is set to the middle hole and I have the receiver set fwd. 81/2" bed rail clearance and tons of room between the tail gate and box sides. Zero issues with cab clearance as well.
I haven't had any issues with bed deflection or the hitch moving in the truck, hitch torqued to 60ft/lbs. Perhaps the bed mat helps or that is just a Ram thing??
Had a Pullrite superglide in my last truck which work flawlessly, hated how heavy it was though. I really love the Andersen!